Synchronizing mechanism for transmission gearing



July 16, 1935. w. R. GRISWOLD 2,008,497

SYNCHRONIZING MECHANISM FOR TRANSMISSION GEARING Filed May 2, 1932 2]W1) M41004: A/HLTEE' E. EEJSNULD.

Patented July 16, 1935 SYNCHRONIZING MECHANISM FOE;

TRANSMESSION GEARING Walter R. Griswold, Detroit, Mich, assignor toPackard Motor Car Company, Detroit, Mich, a corporation of MichiganApplication May 2, 1932, Serial No. 608,663

3 Claims.

This invention relates to motor vehicles and particularly to thetransmission gearing thereof It is moreespecially concerned with thattype of gearing having synchronizing m'echanismwhere- :5 in therelatively sliding elements are by friction devices brought to asubstantiallyuniform, speed before meshing,

Such a synchronizing mechanism usually employs a dash pot device for thepurpose of retardlO' ing the shifting action sufficiently to give therotating parts time to synchronize. Usually the dash pot is of thepiston and cylinder type containing a liquid such as oil, which liquidis forced through a valved port or a passage of predeter- 15 mined sizein causing thedelayed action.

One of the objects of thepresent invention is to provide such asynchronizing mechanism with a supplyof oil or other liquid for the dashpot device.

Another object of the invention is to provide such a synchronizingmechanism with suitable means for assuring escape of air from the dashpot cylinder while at the same time keeping the dash pot suitablysupplied with oil or other liquid.

Other objects of the invention will appear from the followingdescription taken in connection with the drawing, which forms a part ofthis specification, and in which:

Fig. l is a vertical transverse section through a 30 transmissiongearing embodying the invention;

Fig. 2 is a detail View of a portion of the synchronizing mechanismshowing the liquid reservoir in elevation;

Fig. 3 is a view similar to Fig. 2 except that the reservoir issectioned on the line 3--3 of Fig. 4, and

Fig. 4 is a vertical section substantially on the line 44 of Fig. 1.

Referring to the drawing, I represents a transmission gear case in whichthe transmission gears are suitably mounted. One of the transmissionshafts is shown at H and upon this is mounted one of the gear elementsl2. A sleeve l3, splined on the shaft l l, carries an element [4 whichmay be one of the relatively sliding elements for effecting a couplingof the gear parts.

I5 is a shiftable synchronizing member shown in the form of a yoke andpivoted upon eccentrically mounted pivots 16 in the side walls of thegear casing Ill. The eccentric mounting of these pivots makes the yokeadjustable to take up wear or for initial adjustment at the factory.

Pivoted on the yoke in offset relation to the pivots 16 are thrustblocks I! which co-operate with the shiftable elements in any suitableway to effect their operation. 7

Above the yoke 55 are shifter rods l8, one of which is adapted to slidethe sleeve l3 through an arm [9 and the other of which is adapted tooperate similar elements of the gearing which are not shown in thedrawing. One of the rods. l8 also operates the yoke I5 for the purposeof shifting the synchronizing mechanism and the connection. between theyoke and'the rod I8 is through a plunger 28 mounted in the yoke. Thisplunger 20 has a roller 2| mounted in its upper end and this rollerrests in a notch 22 in the rod I8. It will be obvious that shifting therod l8 lengthwise will cause a rocking action of the yoke 15 on itspivots 56 as long as the roller 2| remains in the notch 22. At the sametime, the endwise movement of the rod l8 will carry the arm l9 alongwith it and thereby shift the element l4. By suitably relating theleverages the synchronizing element is first engaged and the clutchelement is meshed after the parts have become synchronized. The timeelement for this synchronizing is governed by a dash pot to which theplunger 20 is connected as will be hereinafter described.

The dash pot device referred to is shown as mounted on the yoke l5 andit is in the form of a cylinder 30 arranged diagonally on one side ofthe yoke. The outer half of this 7 cylinder 30 is bored a little largerthan the inner half and the plunger 20 extends through the outer half ofthe cylinder and into the inner half. A shoulder is formed at 3| and aspring 32 extends from that shoulder to the enlarged part 33 of theplunger 20, thereby constantly pressing the plunger outwardly or intocontact with the notch 22 of the shifter rod It. The plunger 2|] isshown as being hollow but its upper end is closed by a suitable plug 34,and a pin 35 extends outwardly from the plunger and rides in alongitudinal slot 36 in the upper end of the cylinder 30. This slot 36also forms an air outlet at the upper end of the cylinder so that anyair in the dash pot device may escape at that point.

The lower end of the plunger has a piston 31 connected to it by a pin 38and the piston rides in the lower part of the cylinder and, inconnection with the closed end of the cylinder, forms a dash pot. Thepressure below the piston may be relieved by a conical valve 39 held toits seat by a spring 40. This will open the under side of the piston tothe interior of the plunger 2!! and the oil or air may escapetherefromthrough one or more openings 4| just beneath the plug 34.

Formed as an integral part of and shown as partially surrounding thecylinder 3!! is a reservoir 50. The lower part of this reservoircommunicates with the interior of the cylinder at a point above thepiston travel but appreciably below the airoutlet 36. This communicationis through a conduit shown particularly in Figs. 3 and l. It enters thecylinder 39 approximately at the shoulder 3|.

In a dash pot such as this it is particularly desirable that there shallbe no air in the system or if air succeeds in getting in, that it shallbe quickly expelled. Otherwise the dash pot action is interfered withdue to the compressibility of the air. In the present construction the.air is permitted to escape at the top of the cylinder and the oil issupplied to the cylinder near the bottom of the low pressure partthereof. It will be understood that there is suihcient clearance betweenthe piston 31 and the part of the cylinder in which it operates ,topermit the oil to work down past the piston when the spring 32 pushesthe plunger outwardly into the notch 22. In this way the operation ofthe device causes the oil to be pushed slowly out from under the pistonthereby retardingthe action of the shifter rod 18, and then as the rodis reaches a position Where the plunger 20 will enter the same oranother notch the oil will be drawn back under the piston again. Any airin the system escapes through the air outlet 36 and overflow oil alsoescapes into that point and into the reservoir 5%. The supply of oil tothe cylinder is replenished from the reservoir 5% through the conduit 5!which communicates with a low point in the low pressure part of thecylinder. Thus there is a constant tendency to expel the air from thesystem and to keep it constantly replenished with oil for its mostsatisfactory operation.

While I have herein described in some detail a specific embodiment of myinvention, which I deem to be new and advantageous and may specificallyclaim, I do not desire it to be understood that my invention is limitedto the exact details of the construction, as it will be apparent thatchanges may be made therein without departing from the spirit or scopeof my invention.

Having thus described my invention, what I claim and desire to secure byLetters Patent is:

1. In a motor vehicle, the combination of a transmission gearingincluding a shiftable memher, a dash pot device mounted on said memberand having an open air outlet at its upper end, and a reservoir foroperating liquid mounted on said member and connected by a conduit withsaid device below said air outlet, said reservoir being open at itsupper end.

2. In a motor vehicle, the combination of a transmission gearingincluding a shiftable memher, a dash pot device including a cylinder onsaid member and a piston operating in the lower part of the cylinder,there being an open air outlet at the upper end of the cylinder, and areservoir and having an open air outlet at its upper end and having apiston member, and a reservoir for operating liquid mounted on saidmember and connected byia conduit with said device above the travel ofthe piston member and below said air outlet.

WALTER R. GRISWOLD.

